Starcraft 2: Heart of the Swarm is due out by the end of the year, but it's been a while since we heard anything about its development. Blizzard released a video today of the build that will be playable at MLG Anaheim this weekend . It includes some new and some old information, showcasing the units that are still currently making the cut and as well as a few new ones.

The big changes

Among the units removed since the Blizzcon build is the Terran Shredder, a unit that dealt AoE damage to any enemies near it as long as there were no friendly units in the same radius. It has been replaced with the Widow Mine. Built from the Factory, these mines move on their own and, once planted, will stick to the first unit to walk over them and detonate after a few seconds. They have a large splash damage radius, but give a skilled micro player time to move a mined unit away from the rest of their army before it explodes to minimize the damage.

The Terran Warhound seems to have been modified from a light anti-air unit to an "anti-mech" unit, doing relatively little damage to biological foes, but having a very powerful, long-ranged missile attack that can quickly deal with mech units like Thors and Siege Tanks. We're not sure yet whether it will target zerg massive units like the Ultralisk.

Speaking of the Ultralisk, his researchable burrowed charge ability is still intact. The Zerg seem to have changed the least, with their new caster unit, the Viper, remaining more or less the same. The Swarm Host, a new unit that spawns infinite, free, weak minions called Locusts is the only piece that has seen noticeable alteration, in that its Locusts can now attack air units.

The Protoss Replicant, which could transform into any enemy unit on the battlefield, has been removed. The Tempest, which was originally an Air vs Air splash damage specialist has been re-purposed to have longer range and attack air and ground.

The Oracle, a support unit that can lock down enemy mineral patches with a force field, has been given additional utility with a short-ranged cloak similar to the Arbiter from the original Starcraft. It takes over this role from the Mothership, which is now upgraded from a Mothership Core. Rather than being an offensive unit, the Mothership Core can be cost-effective in the early game, and must attach to a Nexus to use its abilities- turning into a super-powerful Photon Cannon, refilling another caster's energy and mass-recalling units to the attached Nexus.

To see some of the Zerg and Protoss changes in action, check out the latest Battle Report casted by Day[9] and Blizzard's Rob Simpson: